Having now proved that the lambda (O2) sensor was probably not working, it was time to do something about it. I had a spare sensor, so the first thing to do was to remove the old one. This turned out to be easier said than done, as it had been in the pipe for about 10 years and was corroded in. So I took it to the local garage who managed to cut it out. The sensor was wrecked in the process but that didn't matter.
While this was going on two things happened. For some months I had been watching a Superspec exhaust, complete with lambda sensor, catalytic converter, silencer and heat shield that was on E-Bay. The owner was gradually reducing the price and it was now down to £75. As the RRP is about £500 I decided it would be a good buy. At the same time someone I was working with on the software program said he had a spare sensor and would post it to me.
So I suddenly found myself with 3 complete exhaust systems with sensors.
First thing to do was to mount the new exhaust pipe and sensor. It looked good, but unfortuately when I took her for a run the sensor did not work at all. That was rather worrying and I wondered if I had a more fundamantal problem.
But the next thing to try was to fit one of the new sensors instead. I was actually quite pleased when I took the old sensor out and it was completely 'coked' up. I suspect the previous owner ran it on his car without the heater connected and it just 'sooted' up.
So took her for a run with the new sensor fitted (with the wires from the sensor and the loom simply twisted together) and this was the result (Shows before, with the original sensor, and after, with the new one):
So we can see the new sensor is working perfectly, rapidly switching between 0.1V-0.9V, which is how it is supposed to be. And just as a check I tried the other sensor I had been given and got an identical result.
So I now have 3 complete exhaust systems, with 2 working sensors and possibly one more if it starts to work after I have cleaned it.